Motor with stator on printed circuit assembly

ABSTRACT

A motor including a stator winding energization circuit on a printed circuit board. Terminals secured to the stator have stator winding ends welded thereto. For purpose of mechanically and electrically connecting the stator and the PC board, the stator is connected to the board in the manner of circuit components, by insertion of the terminals in conforming slots on the board and by wave soldering the tips of the terminals to the board&#39;s conductors.

BACKGROUND OF THE INVENTION

The present invention relates generally to motors such as DC brushlessmotors that have a printed circuit ("PC") board carrying a motorenergization circuit, and more particularly to the manner of assemblingthe stator and PC board.

The manufacture and sale of small motors is a highly price competitiveindustry. Improvements in the manufacturing process which result in costsavings per motor will result in significant commercial advantage in themarketplace. Typically, the stator of a brushless DC motor ismechanically mounted to the PC board by means of motor support posts orlugs and is separately electrically connected to the PC board bysoldering winding ends to connection points on the board. The mechanicalmounting and electrical connection is ordinarily done by hand, which isnot only time consuming but costly. Even if done automatically, theseparate mounting and electrical connection of the stator and PC board,independent of soldering the energization circuit components to theboard, requires too many time consuming steps.

It will be appreciated from the foregoing that a stator simultaneouslymechanically mounted and electrically connected to a PC board in themanner of a circuit component either manually or, preferably, withautomatic equipment such as wave soldering equipment, is a significantand valuable improvement contributing to lower assembly cost and greaterreliability.

SUMMARY OF THE INVENTION

In accordance with the invention, a motor includes a stator core havingat least one stator winding and terminals secured to the stator core,the terminals both mechanically mounting and electrically connecting thestator to a PC board carrying the motor energization circuit. Each endof each stator winding is electrically connected to a terminal.

By inserting the terminals into conforming holes in the PC board, and bysoldering the terminal means to the printed copper conductors of theboard, either manually or, preferably, by an automatic solderingprocess, the motor is mechanically mounted and the stator windings areelectrically coupled to the circuit in a single step. Because automaticequipment is presently available for mechanically mounting components,ordinarily circuit components, such as integrated circuits, resistors,capacitors, etc., to PC boards, and because the soldering can beperformed automatically by a wave soldering process, the mechanical andelectrical connections of the stator to the appropriate conductors onthe board can be done automatically and in one step. Preferably thesoldering of the stator terminals and the soldering of the circuitcomponents in place is accomplished in one wave soldering step. As aresult, the stator and board are mechanically connected, and the statorwinding ends are electrically connected to the PC board circuit in lesstime, with uniform quality, and at less expense. In short, the statoritself is treated as another PC board component and can be soldered tothe PC board at the same time as all other circuit components. This isvery unlike prior practice where, only after the PC board was completed,it was mounted on the stator. In other words, previously, because theprinted circuit was (correctly) considered a component to be "installed"in the motor, and because neither the motor nor its stator was viewed asa circuit component, but as the device that the circuit served, nothought was given to treating the stator as a component to be mounted onthe board for the purpose of mechanical motor assembly and electricalconnection. Hence the stator was not configured for this purpose, e.g.by providing terminals readily wave soldered in place like the leads orpins of circuit components, and, in the case of a brushless DC motor,like the leads of a Hall device used to sense rotor position to controlcommutation of the windings via the energization circuit.

More particularly, the motor's stator includes a lower insulator ofplastic that, in addition to insulating the windings from the statorstack, has sockets formed thereon to receive the terminals snugly inplace. The terminals thus extend from the bottom surface of the lowersupport member. Each terminal preferably includes a tang. Ends of thestator winding are brought under the tang on the appropriate terminals.The winding ends are welded to the terminals, the tang being crimpedonto the underlying wire and fused therewith by the, preferablyautomatic, welding equipment. To further secure the terminals within thesockets on the stator insulator, each terminal end includes a pluralityof barbs extending opposite the direction the terminal is inserted. Theterminals are configured to seat on the board with their tip justprojecting from the remote side thereof where soldering occurs. Thewelding of the winding ends is easily accomplished and in known fashion,for example by using techniques and equipment previously employed toweld winding ends to tangs on commutator bars or rings of motors orother rotary components.

Once combined, the board and stator stack are handled as a singlecomponent of the motor. In the case of an inverted motor, the stator andboard are mounted in a support with a central cylindrical shaftprojecting upward through a central hole in the board and a central holein the stator stack as is conventional. Bearings in the cylindricalshaft then receive the shaft of an external rotor. If the motor is abrushless DC motor, mounting of the rotor brings a commutation magnetpattern into alignment with a Hall device located on the circuit board.

Other aspects and advantages of the present invention will becomeapparent from the following description of the preferred embodiment,taken in conjunction with the accompanying drawings, which disclose, byway of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view, partly in elevation and partly in section, of aninverted, four-pole brushless DC motor in which the stator is connectedby terminals to a printed circuit board.

FIG. 2 is a bottom view of the stator of the motor of FIG. 1 and hasparts removed or broken away for clarity.

FIG. 3 is a perspective view of a terminal for connecting the printedcircuit board and stator of FIGS. 1 and 2.

FIG. 4 is a fragmentary side elevation view of the terminal of FIG. 3 inplace in a socket secured to the stator and schematically illustratesthe welding of the winding end or lead to the terminal.

FIG. 5 is a fragmentary front elevation view of the terminal of FIGS. 3and 4 in place in the socket with a winding end welded in place and theterminal installed and soldered to the printed circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, in FIG. 1 there is shown a brushless DC motor10, comprising a laminated stator core 12, a rotor 14, a lower supportmember 16 and a plurality of terminals 18, which can be easily andreadily connected to a PC board 20. The motor includes stator windings22 wound on the four main stator poles 23 (FIG. 2). Four interpoles 24are located between the main poles. A rotor permanent magnet 25 (FIG. 1)is affixed in a metallic cup 27 that forms the back iron of the rotor.The magnet 25 has a field section 28 and a commutation section 29. Thefield magnet has radially magnetized segments appropriately arranged tointeract with the poles of the stator core to develop torque. Thecommutation magnet section is aligned with a Hall switch 31 supported onthe PC board 20 and electrically connected with a circuit on the boardfor controlling energization of the windings 22 at appropriate points inthe rotation of the rotor 14. The commutation magnet section 29 ismagnetized radially in segments that, as they pass the Hall switch,cause the Hall switch to switch states, energizing and deenergizing theparticular windings via the circuit on the board. Appropriatemagnetization patterns for the field segments and commutation segmentsare disclosed throughout the art and do not form a part of thisinvention. Likewise, numerous energization circuits are describedthroughout the art and the particular circuit is not a part of thisinvention. For simplicity one circuit element 33 is shown connected tothe PC board. The copper conductors 35 of the board can be seen in FIG.1 connected by solder 37 to the leads of the circuit element 33 and theends of the terminals 18.

The stator core 12 has upper and lower insulators 41 and 42. Theseconform to the stator laminations that make up the core 12 and insulatethe windings 22 from the laminations. The lower insulator 42 is bestseen in the illustration of the stator in FIG. 2. The lower insulatorhas main pole insulating projections 44 extending to the ends of themain poles 23 and interpole projections 45 extending along theinterpoles 24. These projections 44 and 45 radiate from a centralring-like flange 46. Vertical walls 47 of the insulator extend alongedges of the stack of laminations. (See also FIGS. 4 and 5) In all ofthe above respects the upper insulator is similar, with main andinterpole projections, and vertical walls that reach down to meet theupward reaching vertical walls of the lower insulator.

A central opening 50 through the stator core 12 receives a cylindricalsleeve 51. This sleeve passes through a central opening (not shown) inthe PC board 20 and is affixed in a central opening (not shown) in thesupport member 16. The sleeve 51 secures the stator in place on thesupport member 16. Bearings 52 (FIG. 2) receive a shaft 53 (FIG. 1)secured to the cup 27 of the rotor 14. A similar bearing in the supportmember 16 can receive the end of the rotor shaft 53.

The terminals 18 are attached to the lower insulator 42, extend outwardand downward as shown, and attach the motor to the PC board. Eachterminal 18 is rigid and electrically conductive and includes a tang 54(FIGS. 3-5) for electrically connecting an end of the stator winding 22to the terminal.

More particularly, and with reference to FIGS. 1 and 2, the lowerinsulator 42 is molded from an insulating plastic. Unlike the upperinsulator 41, the lower insulator includes four downwardly projectingsockets 55 extending from the bottom surface of the insulator'sinterpole projections 45. These receive the four terminals 18, only oneof which is shown in FIG. 2. Each socket 55 includes an opening 56corresponding to the size and configuration of an end 57 (FIG. 3) of aterminal, so that a terminal is snugly received (FIGS. 4 and 5) wheninserted into a socket opening. Barbs 58 on the terminal ends 57 preventdislocation of the terminal.

Best seen in FIGS. 3 to 5, the tangs 54 may be formed by partiallypunched out sections of each terminal bent to extend outward from theterminals. The barbs 58 can likewise be partially cut out and bent toextend opposite the direction that the terminal ends 57 are insertedinto openings 56 in the sockets. A lower end 61 of each terminal 18 isof slightly smaller width than a neighboring medial portion 62 and fitsinto a conforming opening 63 provided in the circuit board 20 (FIG. 5).Shoulders 64 between the end 61 and the portion 62 seat on the uppersurface of the board 20 to locate the terminal correctly with respect tothe board. Cutouts 65 are also formed at lateral edges of the terminal.

In FIG. 4, connection of a winding end or lead 67 to the terminal 18 isshown. A known welding arrangement provides fusion of the copper wire ofthe winding end and the metal of the terminal for instantaneous, secureand electrically conductive connection of the winding to the terminal.The end 67 of the winding is located under the tang 54 on the terminal18. A conductive backing electrode 68, schematically illustrated in FIG.4, is brought into place behind the electrode. A welding tip 70 appliespressure and sufficient electrical current through the tang 54, throughthe winding end 67, and through the terminal portion 18 to the electrode68 to crimp the wire of the winding end in place and to effect a weld asindicated at 72 in FIG. 5. In known manner, a slight depression 73beneath the winding end 67 prevents the tang 54 from shearing the wirethereunder.

Like the components (e.g. circuit element 33) of the circuitry carriedby the board 20, the terminals 18 of the stator 12 are inserted in theirslots 63 in the board and conventional soldering, typically a known wavesoldering technique, is used to apply solder connections 37 between theends 61 of the terminals and the conductors 35, just as the circuitelements have been connected to their appropriate conductors 35.

Unlike prior practice, for the purpose of electrical connection of thewindings to the control circuitry, and for the purpose of physicallyjoining the circuit board and stator, by this invention the stator iscompleted and then mounted as a circuit element, rather than the devicethat the circuit serves, and to which the circuit is ultimately to beconnected. This, then, furthers the objective of rapid, certain, andautomated motor construction.

With the stator 12 and circuit board 20 thus combined, mounting these onthe support 16 and its shaft 51 is easily accomplished, and the angularrelationship of the stator and the commutation controlling Hall switch31 is already correctly fixed.

Although the invention has been described in detail with reference toits presently preferred embodiment, it will be understood by one ofordinary skill in the art that various modifications can be made withoutdeparting from the spirit and the scope of the invention, as set forthin the appended claims.

We claim:
 1. A motor comprising:a stator core; a rotor mounted forrotation relative to the stator core; at least one stator winding woundon the stator core for generating a magnetic field for driving therotor; a plurality of terminals secured to the stator core and extendingaway from the stator core, and having first ends and medial portionsadjacent the first ends, said first ends being smaller in at least onedimension than the medial portions; the winding having ends electricallyconnected to preselected terminals; a printed circuit board; motorenergization circuit means on the printed circuit board; openings in theboard conforming in size and location to the first ends of the terminalson the stator core but being smaller than the medial portions of theterminals; said openings receiving the first ends of terminalstherethrough but not the terminal medial portions, wherein when receivedthe stator core is seated at a selected location relative to the boardwith the medial portion abutting the board; and conductors on the sideof the board remote from the stator having solder connections to thepreselected terminals on the stator core and to electrical connectionmeans of components of the circuit means.
 2. The motor according toclaim 1 wherein welded connections to the terminals electrically connectthe ends of the windings and the preselected terminals.
 3. The motoraccording to claim 2 wherein the preselected terminals have tangsoverlying winding ends, and the tangs are welded to the winding ends. 4.The motor according to claim 1 wherein the stator core has socket meanssecured thereto receiving second ends of the terminals opposite saidfirst ends.
 5. The motor according to claim 4 wherein an insulator onthe stator core has said socket means integrally formed thereon,projecting toward the printed circuit board, and receiving the secondends of the terminals in closely fitting openings therein.
 6. The motoraccording to claim 5 wherein the second ends of the terminals receivedin the openings in the socket means are barbed to prevent dislocation.7. The motor according to claim 5 wherein the insulator is one of twoinsulators on the stator core substantially covering the core andinsulating the winding from the stator core where the core and windingadjoin.
 8. The motor according to claim 1 wherein:the motor is abrushless DC motor having a permanent magnet rotor with field magnetmeans to interact with the stator core to develop torque therebetween,and commutation magnet means; and a Hall device mounted on the circuitboard and electrically connected with the circuit thereon, the Halldevice being aligned with the commutation magnet means of the rotor. 9.The motor according to claim 1 wherein each terminal first end has awidth smaller than the medial portion to form two shoulders at oppositelateral edges of the terminal, and wherein cutouts are also formed inthe terminal edges adjacent said shoulders.
 10. The motor according toclaim 1 wherein the printed circuit board has a selected thickness andwherein each of the terminal first ends have a length longer than thecircuit board thickness so that the first ends extend from the remoteside of the board a selected amount.
 11. A motor comprising:a statorcore; a rotor mounted for rotation relative to the stator core; at leastone stator winding wound on the stator core for generating a magneticfield for driving the rotor; an insulator secured to the stator core andhaving socket means integrally formed thereon and defining openingsextending away from the stator core; a plurality of terminals havingfirst ends extending away from the stator core and second ends closelyfitted into openings of said insulator, said second ends being barbed toprevent dislocation; the winding having ends electrically connected topreselected terminals; a printed circuit board; motor energizationcircuit means on the printed circuit board; openings in the boardconforming in size and location to the terminal first ends, saidopenings receiving the terminal first ends therethrough; and conductorson the side of the board remote from the stator having solderconnections to the preselected terminals on the stator core and toelectrical connection means of components of the circuit means.
 12. Amotor comprising:a stator core; a rotor mounted for rotation relative tothe stator core; at least one stator winding wound on the stator corefor generating a magnetic field for driving the rotor; a plurality ofterminals having first ends extending away from the stator core andsecond ends ecured to the stator core, each terminal having a tang at amedial portion of said terminal between said two ends; the windinghaving ends welded beneath tangs of preselected terminals and withoutencircling said terminals; a printed circuit board; motor energizationcircuit means on the printed circuit board; openings in the boardconforming in size and location to the terminal first ends, saidopenings receiving the terminal first ends therethrough; and conductorson the side of the board remote from the stator having solderconnections to the preselected terminals on the stator core and toelectrical connection means of components of the circuit means.